The invention relates to a composite frame, particularly for use in windows, doors and facades.
Conventional composite frames, as they are commonly known include two metal sub-frames spaced one from another and interconnected by means of an elongated thermally insulated bar inserted into the grooves formed in the sub-frames.
In a previously known frame of this type, (for example disclosed in German Published Application No. 25 52 700), an elongated thermal insulator is made of a plastic material and provided with a special coating to increase the coefficient of friction relative to the metal frames. The coating may comprise a resilient sealing material including additives to increase the coefficient of friction; the additives, for example, may be formed of a fine-grained mineral such as quartz or corundum.
It has been further proposed in German Published Application No. 25 52 700 to provide depressions in the insulator, the depressions being distributed along the length of the insulator in the region where the flanges of the metal sub-frames forming the grooves are to be fixed. Parts of such flanges of the metal sub-frames are deformed into these depressions of the insulator when the sub-frames and insulator are joined together.
The composite frame is provided with good shearing strength by these known measures.
However, it is still desirable to strengthen the composite frames which are composed of relatively light material subjected to deflections when the assembled frame is under loads.